1991 Pontiac Grand Prix HELP!

ANTHONY.KATHREIN

MEMBER
1991 PONTIAC GRAND PRIX
4 CYL
FWD
AUTOMATIC
150,000 MILES

When you try to gain speed you can't. WHen you are trying to drive down the road the engine kinda studders and when you floor it it just goes blaaaahhhh and has no power to go. It is firing on all cylinders there is no problems in the exhaust for they are new from engine back. I have changed the coils, coil housing, ingnition control module, plugs, plug boots, sent a top grade fuel injector cleaner through it, changed the fuel pump, fuel filter, and made sure the fule lines were clear. The exhaust is coming out a little blue and smells like gas and is burning through gas like mad. I know it is firing on all cylinders but I have no clue what is wrong.

4 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Your possibilities here could be:

Oxygen sensor
Catalytic converter
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires

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Monday, November 2nd, 2009 AT 3:31 AM

ANTHONY.KATHREIN

MEMBER
2 POSTS

Oxygen sensor - checked that its still good
Catalytic converter - I told you the exhaust is new from engine back
Dirty fuel injectors (cleaning the injectors often fixes this). - I sent a good fuel injector cleaner through
Bad MAP (manifold absolute pressure) sensor - could be
Bad TPS (throttle position) sensor - nope checked that
Bad or dirty MAF (mass airflow) sensor - don't think my car has one considering NO parts store has one for my car
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump) - just replaced my fuel pump and checked my lines it is pumping fine
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve) - I can't find any vaccum leaks I checked all the lines I could find
Bad gasoline (fuel contaminated with water or too much alcohol) - I have added additives to aleviate the water if there is some and it has been happening for a while now

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs - brand new plugs
Bad plug wires - there are no wires just boots and those are new
Weak ignition coil - just changed the coil
Wet plug wires - like I said there are no wires

And I still have problems

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Monday, November 2nd, 2009 AT 11:24 AM

RASMATAZ

MECHANIC
75,992 POSTS

Low fuel pressure (leaky fuel pressure regulator or weak fuel pump) - just replaced my fuel pump and checked my lines it is pumping fine

You need to actually check the fuel pressure if its within specs it doesn't matter whether its new-You sure the transmission is not slipping

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Monday, November 2nd, 2009 AT 11:32 AM

ANTHONY.KATHREIN

MEMBER
2 POSTS

Wouldn't there be signs of tranny slip like sounds and things like that. I have listened for tranny problems ever since this started to happen. It also does it now in idle when I hit the gas it bogs down and wants to die. How do I check the pressure considering I live 45 miles from any autoparts store or mechanic and have no way to get it there.

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Monday, November 2nd, 2009 AT 11:43 AM